Ultra high frequency oscillation generator



B. D. LOUGHLIN 2,472,598

ULTRA HIGH FREQUENCY OSCILLATION GENERATOR June 7, 1949.

Filed March 1, 1945 22 FIGAQ W7 22 5 l FIG.6

QUYENCH- FREQUENCY AMPLIFIER DETECTO R INVENTOR. BERNARD o. LOUGHLIN ATTORNEY Patented June 7, 1949 ULTRA HIGH FREQUENCY OSCIL- LATION GENERATOR Bernard D. Loughlin, Bayside, N. Y., assignor, by 'mesne assignments, to Hazeltine Research, Inc, Chicago, 111., a corporation of Illinois Application March 1, 1945, Serial No. 580,375

I 12 Claims. 1

This invention is directed to ultra-high-frequency oscillation generators. While being subject to a variety of applications, the invention is especially suited for use in a wave-signal receiver of the superregenerative type and will be particularly described in that connection.

As is well understood in the art, a superregenerative receiver essentially comprises a regenerative circuit which has positive and negative values of conductance during alternate operating intervals. The conductance variations are usually controlled by a periodic quench voltage of relatively low frequency and for stable operation the circuit conductance, integrated over a period of time long with reference to the period of the quench voltage, has a positive value. Durin negative-conductance intervals, transient oscillations are produced in the regenerative circuit which build up exponentially during each such interval and attain a maximum amplitude determined by the amplitude of the signal which initiates the oscillations. The initiating signal may be a received signal or, in the absence of received signals, may be supplied by the noise signals inherent in the regenerative circuit. In either I case, the oscillations generated in one negativeconductance interval are suppressed or damped during the next succeeding interval of positive conductance. Thus, the receiver may be considered as an oscillation generator having an interru-ptecl, as distinguished from a continuous, operation and producing transient oscillations which vary in accordance with the exciting signal, Such a recever has two outstanding characteristics: (-1) the regenerative circuit has an exceedingly high gain so that received signals are amplified to an unusually high-degree, and (2) in the usual installation the receiver radiates an output signal termed a quiescent signal in the absence of received signals.

When receivers f the type under consideration are to be operated at ultra-high frequencies, certain difilculties are encountered in their construction. For example, conventional oscillatory circuits which have been utilized in prior art arrangements do not permit optimum operation to be realized. This results from the fact that inherent circuit reactances, such as lnterelectrode capacitances and electrode-lead inductances, represent appreciable reactances 'at ultra-high afrequencies which have .a pronounced effect on the operating characteristics of the oscillator and, in the usual case, impair its operating characteristics.

Also, in some installations it is desirable to prevent the receiver from transmitting its quiescent signal during operating intervals when no signals are being received. To obtain this result, it has been proposed that a radio-frequency amp'lifier or buffer stage be interposed between the regenerative circuit and its receiving antenna. At the frequencies involved, a very practical buffer stage for this purpose is the cathode-input or grounded-grid amplifier, wherein the input and output circuits are effectively shielded without the necessity of elaborate neutralizing circuits. In the prior arrangements such a buffer stage has been coupled capacitively or inductively to the regenerative circuit. However, the inherent reactances of the output circuit of the buffer stage in these arrangements reflect undesirable reactance components into the regenerative circuit and difiic'ulty has been experienced in providing efllcient coupling between the buffer and regenerative circuits.

It is an object of the present invention, therefore, to provide an improved ultra-high-frequency oscillation generator which substantially avoids the above-mentioned limitations of prior art arrangements.

It is another object of the invention to provide an improved ultra-high-frequencyoscillation generator which makes effective use of its inherent circuit reactances.

It is a further object of the invention to provide an improved ultra-high-frequency oscillation generator especially adapted to be included in a superregenerative receiver in cascade with a buffer stage.

An ultra-high-frequency oscillation generator, in accordance with the present invention, comprises an electron-discharge device having anode and cathode electrodes and an intermediate control electrode maintained at a .fixed reference potential. The generator includes resonantcircuit means having a voltage-divider tap coupled to the control electrode of the electrondischarge device and a phase-shifting vnetwork including at least one element which is serially connected with the resonant-circuit means -between the anode and cathode electrodes of the electron-discharge device. The phase-shifting network, in conjunction with the resonant-circuit means, provides input and output circuits for the electron-discharge device effective to feed back energy from the output circuit to the input circuit with such phase as to support sustained oscillations at an operating frequency corresponding substantially to the resonant frequency of the resonant-circuit means.

For a better understanding of the present invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims.

In the drawing, Fig. 1 is a schematic circuit diagram of the alternating current circuits of an oscillation generator in accordance with the invention; Fig. 2 is a vector diagram utilized in explaining the operation of the Fig. l arrangement;

3 represents a modification of the Fig. 1 arrangement; Figs. 4a and 4b are schematic circuit diagrams, while Fig. 5 is a vector diagram, utilized in describing a particular operating characteristic of the oscillation,- generators of Figs. 1 and 3; Fig. 6 is a further modification of the Fig. l arrangement; and Fig. '7 represents a complete superregenerative receiver including an oscillation generator in accordance with the invention.

Referrin now more particularly to Fig. 1, there are represented the alternating current circuits of an oscillation generator, adjustably tuned for operation over a desired range of ultra-high frequencies. This generator comprises an electrondischarge device, specifically a triode vacuum tube l9, having anode and cathode electrodes and an intermediate control electrode which is rounded so as to be maintained at a fixed reference potential. Tube ['0 is selected of such construction as to have a control-electrode lead of negligible inductance. A resonant-circuit means including a capacitive-type voltage divider having a tap coupled to the control electrode of tube iii constitutes the frequency-determining circuit of the generator. This resonant-circuit means includes a variable inductor H tuned by seriesconnected condensers l2 and I3. The common terminals of condensers l2 and I3 are directly connected to the control electrode of tube Ill.

The generator also comprises a phase-shifting network including at least one reactance element of a first type serially connected with resonant circuit H, 12, 1'3 between the anode and cathode electrodes of tube and at least one reactance element of a second type efiectively connected between the control electrode and one of the anode and cathode electrodes of tube [0. As illustrated, this phase-shifting network comprises an inductor i i coupling one terminal of the frequencydetermining circuit with the cathode of tube i8 and a condenser it: connected between the control electrode and cathode of tube ID. This phaseshifting network is series-resonant at a frequency substantially difierent from the operating frequency of the generator and, in conjunction with the frequency-determining circuit thereof, provides input and output circuits for tube ii] efiective to feed back energy from the output circuit to the input circuit with such phase as to support sustained oscillations at an operating frequency corresponding substantially to the resonant frequency of the frequency-determining circuit. The output circuit, coupled between the anode and cathode electrodes of tube l3, includes resonant circuit ii, 3 l3, while the input circuit, coupled lz etwe n the cathode and c. electrodes, includes condenser 53 i1. CO? output circuit for feedin back one output to the input circuit.

considering the operation of the described arrange icnt, let it be assumed that the circuit oscilla -ng, producing circulating c ll'lfGllllS in resonant circuit ll, l2, E3. The resulting vol' 'gc Cp established across condenser if: at sta'ot in opposition to the vol 'tablislied across condenser i3 and utilize. a fee-baa: vol The feed-back ro duces a current flow in phase-shifting netit- M, 55 which is represented by vector i Fig. 2. The phase-shifting network is series-res a frequency much less than the operating frequency of the generator so that a voltage 6: of relatively large magnitude and leading the current through the phase-shifting network by 9i) degrees is produced across inductor Hi. A voltage at which lags the current by 90 degrees is established across condenser 15. The vector sum of the voltages c1 and 80 represents the driving voltage es of the phase-shiftin network. Thus, it will be seen that the voltage Cc between the cathode of tube It and ground, or effecti czy between the cathode and control electrodes of the tube, is in phase opposition to the driving voltage 80 and, hence, is in phase with the voltage ep. Therefore, the voltage variations of the anode and cathode electrodes, referred to the grounded control electrode, are in phase, which is the proper phase relation required to support sustained oscillations at a frequency eorresponding substantially to the resonant frequency of the circuit ll, i2, H3.

The described oscillation generator is particularly suited to take advantage of the inherent reactances associated with vacuum tube it. These reactances include the self-inductances oi the electrode leads conventionally utilized for maleing circuit connections to the tube and the inherent interelectrode capacitances. The circuit arrangement of Fig. 3 is a modification of the Fig. 1 generator demonstrating the manner in which such inherent reactances may be conveniently utilized.

In Fig. 3 the terminals 20, 2| and 22 are intended to designate the terminal prongs which are coupled by way of electrode leads 23, 2 and 25 to the anode, control electrode, and cathode, respectively, of tube H). In this embodiment of the invention, the inductive reactance of the described resonant-circuit means includes variable inductor l l as well as an inductor 26, represented in broken-line construction since it consists of the self-inductance of the anode-electrode lead 23. The tuning capacitance of the resonant-circuit means again includes condenser l3 serially connected with a condenser l2, shown in brokenline construction since it comprises the anodecontrol electrode capacitance of tube H]. In like manner, the inductor M of the phase-shifting network is provided by the self-inductance of the cathode-electrode lead 25, while the condenser l5 consists of the interelectrode capacitance of the control electrode and cathode of tube I 0. This circuit will be seen to be the full electrical equivalent of that of Fig. 1 and its operation will be evident from the foregoing description. The advantage of the Fig. 3 arrangement resides in its effective use of the inherent circuit reactances which otherwise may materially impair the operating estates.

efiiciency of the; circuit.. While inductor 14; as been. represented: as the inherent inductance; of: cathode lead 25.. an; external inductance; also be included inthe: cathode. GmQ m sup ementing the inherent inductance thereof, where the inherent, inductance is; insufiicient, to- Ell-Guide the desired, resonant freduency of; the; phase-shitting network.

The description thus far has taken into con. sideration only the. inductive and capacitive reactances ofi'the; input. circuit of; tube. Ht. It-will; be appreciated that the tube has a predetermined input conductance, that is, the conductance be.- tween its cathode and control electrodes. Where the: input conductance constitutes an appreciable impedance elementof the input circuit, thephasa shifting: network- M, t5 has the form represented schematically in Fig. 4a; where the resistance 39 represents the input conductance. In acc.ord ance with well-knowntransformation theories, the circuit of Fig. 40.. may be reconstructed as illustrated in- Fig. 4b where the; condenser t5 and resistor 38- replace elements l5 and 30 of Fig. 4a. Through appropriate selection of elements t5."- and 30 the characteristics of the schematic cir-- cuits of Figs. 4a and 4b are identical.

The phase relations of the voltages established in the generator circuit, Where the phase-sh-ift-- ing network is: as represented in. Fig. 4b, are illustrated by the vector diagram of Fig. 5. Current flow through the. phase-shitting network Produces. voltage or across inductor Ml, voltage. e0 across condenser l5,"', -and voltage o across resistor 30, the latter being in. phase. with the. current 2" flowing through the network. The; addition of volttage vectors cc and er shows the voltage-er established between the cathode; and control electrodes to have a phase angle with reference, to, vector or which is difierentfrom- 180 de rees; The driving voltage as of the phase-shifting. network maybe determined. by the vector addition of. the vectors a and er. It will be. apparent that since the oath-- ode-control-electrode voltage eushould preferably be in phase oppositionto; thedrivin volta e at the phase-shifting. network, it is desirable to in.- troduce an additional phase displacement to compensate for the effect of the input conductance of tube it. To this end, a tune-delay network at is included in the phase-shifting network of the generator, as illustrated in Fig. 6. In this representation, time-delay network. 3i. is interposed between inductor M! and the; teed-back condenser L3. The. circuit of 6 is otherwise the same as that of Fig. 3: and corresponding com,

ponents. areidentified by the. samereferencecha actors. The required time-delay network. 3t may. readily be constructed by enclosing, a coil, such as a signal choke, within a grounded metal foil. This construction efiectivelyconstitutes a trans! mission-line section and proportioned to; efiect.

the desired time delay in the phase-shitting net.- work so that the voltage er of Fig. 5- ultimately established between the control electrode. and cathode of tube H) is out of phase; with the driving voltage on of the phase-shifting network.

Referring now to- Fig. '1, thereis represented a, complete signal-translating system, specifically, a superregenerative receiver, including an. oscil-. lation generator in accordance with the present invention. The receiver comprises an antenna system to coupled by meansof acoaxialtransmits sion-line section M- to the; input circuit of a res. peater or grounded grid-amplifying stage. This stage is provided, by avacuum tube. 4.2- haymg: an anode, an intermediate control electrode. main- Jill:

tained: at. ground potentiah and. a cathode. input circuit of tube 42 includes a. cathode resifilluil 43;. connected between the; cathode electrode. of tube42 and ground. to which the antennasystem' is: coupled. A source of space current indicatedl +B,. is coupled to the anode electrode of" tube: 4.2: through a resistor 4.4;, a radio-frequency Sig ali choke t5, by-passed to ground by a condenser- 4:6; terminalprong: 4.1; or the tube and its anode-elect. trode lead: 48. Inductor 9, shown in, brokenrline construction, represents the self-inductance Qi lead. 48;.

The regenerative circuit, conventionally in.- cluded in a superregenerative receiver as pointed out above, is in the form of, an oscillation gener atorof the. type represented in Fig. 6} and, cor responding components thereof are; identifiedby the same reference characters. The inductive reactance of the resonant-circuit. means includes the variable; inductor provided. by a. single turn of metallic ribbon which may betuncd'. in. a well-known manner by a. tuning. plungerad iusu able into, and out of the, plane ofv the inductor; Inductor I I; is directly coupled between anodete-rminal 29 of tube Ill and anode terminals-l: of tube 42. Hence, the inductive reactance of: the rest nant-circuitmeans also includes. the: sold-inductances of the anode-electrode leads of the. oscilsv lator tube to. and repeater tube 3:2; The. capacitance of the,- resohant-circuit means cone prises the condensers l2" and l'3z,, shown in: broken-line. construction since they. comprise the anode-control electrode capacitanccs of tubes: $31 and 42, respectively;

Tube ID, in the arrangement under considerate tion, is provided with a pair of terminals 2.1%,.2l' individually coupled with its. control electrode. Terminal 2| is grounded. through a. condenser 5i: representing a. short circuit at any desired. oper ating frequency of the oscillation generator and terminal 2;! is similarly grounded through a corn denser 5'2. Condenser 52; consists of a groundrrd metal foil surrounding the lead coupled to; terminal 2l-1 so that the control ele rode may grounded for radio-frequency while. has

inga. required direct current path. The direct current paths of tube hi are completed a radio-frequency choke 5'4. and bias resistor til coupled'to. the cathode of tube it, as t l/811185.211 grid resistor 56. A blocking condenser included; in the phase-shifting network oi the oscillation generator;

A- quench-frequency oscillator to, coupled to the input circuit of tube Ill through an isolating re sister 521,, supplies ouenchvoltage for varying the conductance of the oscillation generator circuit in amanner to provide;superregeneration. While oscillator Bil may be of any conventional design and: construction, it preferably supplies a quench voltage: oil sinusoidal: wave form'having a ire-r quency-thatislow with reference tothe operating frequency of. tube It: but. high with reference to: the highestv modulation. component or a received signal to be translated. Condenser 52 in the ill-- put circuit of tube It; while grounding the corp, trolelectrode thereof at the operating frequency of the receiver, presents a high impe. .,nce to the quench voltage.

A, detector 61 is coupled to the resonant-clecuitmcans. of tube I'll through a. conductor ,:to derive an, utput signal therefrom by detecting; the. generated transient oscillations. an ampliffier 63, coupled to the output circuit of detector- Bl, supplies. the. output signal of the receiver .to'

a suitable utilizing device (not shown), as indicated by the arrow 64.

The operation of the receiver of Fig. 7 is generally the same as that of any conventional superregerenative receiver and will be understood by those skilled in the art. The circuit arrangement, however, differs from those of the prior art in that there is a direct coupling between the repeater or buffer stage 42 and the regenerative circuit of tube ID. This avoids the necessity of complex coupling circuits and through the utilization of a grounded grid tube 52, wherein the input and output circuits are effectively shielded, the arrangement is prevented from transmitting its quiescent signal in the absence of received signals. Additionally, the inherent impedances of tube in and those of the output circuit of tube 42 are employed as elements of the frequencydetermining circuit of tube 10.

In each of the several modifications of the invention, the phase-shifting network is utilized for coupling the resonant-circuit means to the cathode of the oscillator tube. However, it will be understood that the phase-shifting network may, if desired, couple the resonant-circuit means to the anode electrode of the oscillator tube.

While there have been described what are a; present considered to be the preferred embodiments of this invention, it will be obvious to those skilled in the art that various changes and moclifications may be made therein without departing from the invention, and it is, therefore, aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. An ultra-high-frequency oscillation generator comprising, an electron-discharge device inculding anode and cathode electrodes and an intermediate control electrode maintained at a fixed reference potential, resonant-circuit means having a voltage-divider tap coupled to said control electrode, and a phase-shifting network including at least one element serially connected with said resonant-circuit means between said anode and cathode electrodes and providing in conjunction with said resonant-circuit means input and output circuits for said electron-discharge device efiective to feed back energy from said output circuit to said input circuit with such phase as to support sustained oscillations at an operating frequency corresponding substantially to the resonant frequency of said resonant-circuit means.

2. An ultra-high-irequency oscillation generator comprising, an electron-discharge device including anode and cathode electrodes and an intermediate control electrode maintained at a fixed reference potential, resonant-circuit means having a voltage-divider tap coupled to said control electrode, and a phase-shifting network series-resonant at a frequency substantially different from the operating frequency of said generator and including at least one element serially connected with said resonant-circuit means between said anode and cathode electrodes and providing in conjunction with said resonantcircuit means input and output circuits for said electron-discharge device effective to feed back energy from said output circuit to said input circuit with such phase as to support sustained oscillations at an operating frequency corresponding substantially to the resonant frequency of said resonant-circuit means.

3. An ultra-high-frequency oscillation generator comprising, an electron-discharge device including anode and cathode electrodes and an intermediate control electrode maintained at a fixed reference potential, resonant-circuit means including a capacitive Voltage divider having a tap coupled to said control electrode, and a phase-shifting network series-resonant at a frequency substantially less than the operating frequency of said generator and including at least one element serially connected with said resonant-circuit means between said anode and cathode electrodes and providing in conjunction with said resonant-circuit means input and output circuits for said electron-discharge device effective to feed back energy from said output circuit to said input circuit with such phase as to support sustained oscillations at an operating frequency corresponding substantially to the resonant frequency of said resonant-circuit means.

4. An ultra-high-frequency oscillation generator comprising, an electron-discharge device including anode and cathode electrodes and an intermediate control electrode maintained at a fixed reference potential, resonant-circuit means having a voltage-divider tap coupled to said control electrode, and a phase-shifting network including a reactance element of a first type serially connected with said resona-nt-circuit means between said anode and cathode electrodes and a reactance element of a second type effectively connected between said control electrode and one of said anode and cathode electrodes, said phaseshifting network providing in conjunction with said resonant-circuit means input and output circuits for said electron-discharge device effective to feed back energy from said output circuit to said input circuit with such phase as to support sustained oscillations at an operating frequency corresponding substantially to the resonant frequency of said resonant-circuit means.

5. An ultra-high-frequency oscillation generator comprising, an electron-discharge device including anode and cathode electrodes and an intermediate control electrode maintained at a fixed reference potential, resonant-circuit means including a capacitive voltage divider having a tap coupled to said control electrode, and a phase-shifting network including an inductor serially connected with said resonant-circuit means between said anode and cathode electrodes and a condenser effectively connected between said control electrode and one of said anode and cathode electrodes, said phase-shifting network providing in conjunction with said resonant-circuit means input and output circuits for said electron-discharge device effective to feed back energy from said output circuit to said input circuit with such phase as to support sustained oscillations at an operating frequency corresponding substantially to the resonant frequency of said resonant-circuit means.

6. An ultra-high-frequency oscillation generator comprising, an electron-discharge device including anode and cathode electrodes and an intermediate control electrode maintained at a fixed reference potential, resonant-circuit means having a capacitive voltage-divider tap coupled to said control electrode, and a phase-shift n v network including an inductor serially connected with said resonant-circuit means between said anode and cathode electrodes and a condenser effectively connected between said control electrode and said cathode electrode, said phase shifting network providing in conjunction with said resonant-circuit means input and output circuits for said electron-discharge device effective to feedback energy fromisaid output circuit to said input circuit with such phase as to support sustained oscillations at an operating frequency corresponding substantially to the resonant frequency of said resonant-circuit means.

'7. An ultra-high-frequency oscillation generator comprising, an electron discharge device aincluding-a-n 'anode, 9, cathode :and an intermediate control electrode maintained at -a fixed reference .pctential jand having electrode leads for making circuit connections thereto, resonant-circuit means connected between said anode and cathode electrodes so as to have an inductive reactance including the self-inductance of at least one of said electrode leads and a capacitive reactance including the interelectrode capacitance between said control electrode and at least one of said anode and cathode electrodes, said resonant-circuit means having a voltage-divided tap coupled to said control electrode, and a phase-shifting network including at least one element serially connected with said resonant-circuit means between said anode and cathode electrodes and providing in conjunction with said resonant-circuit .11: input and output circuits for said electronharge device elfective to feed back energy said output circuit to said input circuit with such phase as to support sustained oscillations at an operating frequency corresponding substantially to the resonant frequency of said resonantcircuit means.

8. An ultra-high-frequency oscillation generator comprising, an electron-discharge device including an anode, a cathode, and an intermediate control electrode maintained at a fixed reference potential and having electrode leads for making circuit connections thereto, resonant-circuit means connected between said anode and cathode electrodes and having a voltage-divider tap connected to said control electrode, and a phaseshifting network including the self-inductance of the electrode lead and the interelectrode capacito said control electrode of one of said anode and cathode electrodes and providing in conjunction with said resonant-circuit means input and output circuits for said electron-discharge device effective to feed back energy from said output circuit to said input circuit with such phase as to support sustained oscillations at an operating frequency corresponding substantially to the resonant frequency of said resonant-circuit means.

9. An ultra-high-frequency oscillation generator comprising, an electron-discharge device including an anode, a cathode, and an intermediate control electrode maintained at a fixed reference potential and having electrode leads for making circuit connections thereto, resonant-circuit means connected between said anode and cathode electrodes so as to have an inductive reactance including the self-inductance of said anode-electrode lead and a capacitive reactance including the interelectrode capacitance of said anode and control electrodes and having a voltage-divider tap connected to said control electrode, and a phase-shifting network including the self-inductance of said cathode-electrode lead and the interelectrode capacitance of said cathode and control electrodes and providing in conjunction with said resonant-circuit means input and output circuits for said electron-discharge device effective to feed back energy from said output circuit to said input circuit with such phase as to support sustained oscillations at an operating frequency corall 1'0 responding substantially to the resonant frequency pf said resonant-circuit means.

1 0. Anwtra high frequency oscillation-generator comprising, an electron discharge device including an an'od'e, a cathode, and an intermediate control electrode maintained at a fixed reference potential and having a predetermined control electrode-cathode'mnductance, resonant-circuiit means having a voltage-divider tap coupled to said control electrode, and :a phase-shifting network h'aving at ieast one -=el'ement serially connected with said resonant-circuit means between said anode and cathode electrodes and including 'a "time-delay network Pier compensating said control electrode-"cathode cor rduetance, :sai'd phaseshi'ft'ing network prawn-st conjunction with said resonant-circuit means input and output circuits for said electron-discharge device efiective to feed back energy from said output circuit to said input circuit with such phase as to support sustained oscillations at an operating frequency corresponding substantially to the resonant frequency of said resonant-circuit means.

11. In a signal-translating system including a repeater having an anode, an intermediate control electrode maintained at ground potential, a cathode, and electrode leads for making circuit connections thereto, an ultra-high-frequency oscillation generator comprising, an electron-discharge device including an anode, a cathode, and an intermediate control electrode maintained at ground potential and having electrode leads for making circuit connections thereto, resonant-circuit means having an inductive reactance coupled between said anode electrodes of said repeater and said electron-discharge device so as to include the self-inductance of said anode-electrode leads thereof and having a capacitive reactance including the anode-control electrode capacitance of said electron-discharge device in series with the corresponding capacitance of said repeater so that said control electrode of said electron-discharge device is effectively connected to a voltage-divider tap of said resonant-circuit means, and a phaseshifting network including at least one element serially connected with said resonant-circuit means between said anode and cathode electrodes of said electron-discharge device and providing in conjunction with said resonant-circuit means input and output circuits for said electron-discharge device effective to feed back energy from said output circuit to said input circuit with such phase as to support sustained oscillations at an operating frequency corresponding substantially to the resonant frequency of said resonant-circuit means.

12. In a signal-translating system including a repeater having an anode, an intermediate control electrode maintained at ground potential, a cathode, and electrode leads for making circuit connections thereto, an oscillation generator for operation over a predetermined range of ultrahigh frequencies comprising, an electron-dis charge device including an anode, a cathode, and an intermediate control electrode maintained at ground potential and having electrode leads for making circuit connections thereto, tunable resonant-circuit means having a variable inductor coupled between said anode electrodes of said repeater and said electron-discharge device so as to include the self-inductance of said anodeelectrode leads thereof and having a capacitive reactance including the anode-control electrode capacitance of said electron-discharge device in series with the corresponding capacitance of said 11 repeater so that said control electrode of said electron-discharge device is effectively connected to a voltage-divider tap of said resonant-circuit means, and a phase-shifting network including at least one element serially connected with said resonant-circuit means between said anode and cathode electrodes of said electron-discharge device and providing in conjunction with said resonant-circuit means input and output circuits for said electron-discharge device efiective to feed back energy from said output circuit to said input circuit with such phase as to support sustained oscillations at an operating frequency corresponding substantially to the resonant frequency of said resonant-circuit means.

BERNARD D. LOUGHLIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,030,120 Rust et a1 Feb. 11, 1936 2,034,433 Heintz Mar. 17, 1936 2,192,306 Graffunder Mar. 5, 1940 2,203,085 Flechsig June 4, 1940 2,284,372 Crosby May 26, 1942 

